An enzyme-linked immunosorbent assay (ELISA) for human chorionic gonadotropin has been developed. Results with this hCG ELISA have been compared with those from an established radioimmunoassay (RIA) and correlation coefficients of R=0.95 and R=0.93 were obtained for serum and urine, respectively. An RIA for growth hormone releasing factor (GRF) has been developed which is capable of determining GRF levels in serum of patients receiving GRF in experimental protocols. Efforts are continuing to improve sensitivity of the assay and to overcome nonspecific serum effects often encountered. Teaching of radioimmunoassay methodology for polypeptide hormones as well as other laboratory procedures required for ongoing projects has been provided for Branch Fellows and others. Sheep anti-rabbit gamma globulin sera (second antibody) was generated, titered and distributed to NICHD Intramural Investigators.